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The posterior tether in scoliosis
J G Jarvis1, R B Ashman, C E Johnston
1University of Ottawa, Children's Hospital of Eastern Ontario, Canada.
Clinical Orthopaedics and Related Research
|February 1, 1988
Summary
Idiopathic scoliosis may be caused by localized lordosis, or tethering of spinal elements. This tethering leads to characteristic vertebral rotation observed in scoliosis patients.
Area of Science:
- Orthopedics
- Biomechanical Engineering
- Spinal Anatomy
Background:
- Idiopathic scoliosis is a complex spinal deformity.
- The etiology of vertebral rotation in scoliosis remains incompletely understood.
- Previous theories have not fully explained the characteristic rotational patterns.
Purpose of the Study:
- To investigate the hypothesis that localized posterior spinal element tethering (lordosis) causes vertebral rotation in idiopathic scoliosis.
- To determine if spinal tethering can replicate the rotational patterns seen in idiopathic scoliosis.
- To explore the biomechanical basis of idiopathic scoliosis using a geometric model.
Main Methods:
- Anatomic specimens of human and calf spinal columns were used.
- Specimens were subjected to axial loading with and without posterior tethering (Zielke instrumentation).
- Lateral deflection and axial rotation were measured using radiography.
Main Results:
- Tethered spines exhibited increased rotation consistent with idiopathic scoliosis.
- In tethered spines, spinous processes moved towards the concavity at the apex of the induced lateral curve.
- Untethered spines showed minimal rotation or rotation towards the convexity, characteristic of rotational kyphosis.
Conclusions:
- The hypothesis that idiopathic scoliosis involves rotational lordosis due to posterior element tethering is supported.
- Spinal tethering can induce the characteristic vertebral rotation observed in idiopathic scoliosis.
- A geometric model can explain the observed rotational mechanics in idiopathic scoliosis.